The present invention relates to a connector socket for making electric connection upon insertion of a plug thereinto, and more particularly to a connector socket designed to prevent electric circuits connected thereto from being affected by electric charges stored in the conductor pins of a plug inserted in the connector socket.
It is customary practice to electrically connect a video camera and a video tape recorder to each other by inserting a plug coupled to a cable of the video camera into a connector socket mounted on the video tape recorder. There are instances where the plug connected to the video camera is electrically charged for some reasons. When the plug with its electrically charged conductor pin is connected to the socket of the video tape recorder, the charge is discharged through electric circuits in the video tape recorder to damage or destroy an IC in the video tape recorder.
To protect the circuit in the video tape recorder, the plug and the connector socket have electrically conductive outer shells made of metal, with the conductive pin of the plug being covered with the conductive outer shell, so that when the plug is placed in an electric field, the outer shell is charged, but the conductive pins are prevented from being charged. Any charge induced in the plug outer shell when the plug is inserted into the socket is drained to a grounding circuit in the video tape recorder through the socket outer shell which is in contact with the plug outer shell.
The conductive outer shells of the plug and socket are generally in the form of die castings for the reason that since the outer shells are relatively complex in shape, they could not be manufactured by a less costly process such as pressing. Therefore, the plug and the connector socket with metal outer shells have been expensive.
The plug covered with the metal outer shell can shield the conductive pins from an exterior electric field to prevent the conductive pins from being electrically charged. However, there may be a condition in which a wire connected to the plug cable is subjected to an electric field generated in the video camera and hence is electrically charged. Should this happen, the conductive pins of the plug are electrically charged regardless of the fact that the plug outer shell is made of metal. The charge in the wire will be discharged through the circuit in the video tape recorder when the video camera is connected to the video tape recorder, resulting in the danger of damage to the IC in the video tape recorder.
Therefore, even with the metal outer shell of the plug, it has not been possible to eliminate electric charges generated in the video camera and to prevent the IC in the video tape recorder from being damaged.